The use of mobile stations such as cellular telephones, personal digital assistants, pagers, or portable computers has become an increasingly popular means of communicating with others, accessing information, conducting business, and performing myriad other activities. Mobile stations typically communicate with cellular wireless networks. These mobile stations and cellular wireless networks communicate with each other over a radio frequency (RF) air interface using any of a number of communication protocols, such as evolution data optimized (EV-DO), WiMax, code division multiple access (CDMA), and other protocols.
A typical cellular wireless communication system is formed by dividing a geographic area into a set of cell sites defined by an RF radiation pattern from one or more base stations. The base stations of the cells may then be coupled to a switching system that connects the base station to a network, such as a transport network or a signaling network. Generally, when a mobile station is powered on and positioned in a cell, the mobile station may communicate with a base station within the cell via an RF air interface. Once connected to the base station through the air interface, a communication path can be established between the mobile station and the network. In this typical arrangement, one or more base stations and switching systems function as a radio access network (RAN) and enable the mobile station to communicate with a network, facilitating the transmission and receipt by the mobile station of voice calls, internet communications, and other data.
In general, the air interface used for communications from a base station to mobile stations, known as the forward link, may be divided into a plurality of channels, including traffic channels used to carry bearer traffic such as voice or other data, and control channels used to carry overhead messages. The protocol used to facilitate wireless communication between the base station and the mobile station may define a number of parameters regarding the overhead messages transmitted in the control channel, such as the type and content of the overhead messages, as well as a schedule defining how often the particular content must be transmitted. For example, the transmission of information in the control channel may be divided into control channel cycles, defined by a certain capacity based on the time allotted for transmission and the transmission rate.
In one protocol known as EV-DO, which stands for “Evolution Data Optimized” and defined by IS-856, a mobile station is typically referred to as an access terminal, and the network entity with which the access terminal communicates over the air interface is known as an access node. The access node typically includes a radio network controller (RNC), which is similar to a base station controller in other network arrangements. The access node also includes one or more base transceiver stations (BTSs), also known as “Node-Bs,” each of which include at least one antenna that radiates to define respective wireless coverage areas. Among other functions, the RNC controls one or more BTSs, and acts as a conduit between the BTSs and other network entities such as a packet data serving node (PDSN). The PDSN typically provides access to a packet-data network (PDN). In combination, an access node and a PDSN can act as a RAN and facilitate communication over an air interface between an access terminal and a PDN.
Among other information, access nodes can transmit control information to access terminals over a control channel, which takes the form of certain timeslots on the forward link. An individual control channel cycle can carry a number of messages, including a quick configuration (QC) message, a sync message, an access parameters (AP) message, a system parameters (SP) message, and page messages. Typically, the SP message includes a list of neighboring coverage areas to which handoff from the current coverage area may occur. Since this neighbor list may vary in size depending on the number of neighbors a coverage area has, the SP message may also vary in size. Under the requirements of IS-856, the QC message must be sent in every control channel cycle, the AP and sync messages must be sent at least once every four cycles, and the SP must be sent at least once every five cycles. Consequently, the amount and content of the information sent in the control channel can vary from control channel cycle to control channel cycle.